A range of diseases, medications, trauma and other factors can lead to a person having motion symptoms such as dyskinesia, in which the person is in a hyperkinetic state, or bradykinesia, in which the person is in a hypokinetic state.
For example, bradykinesia is a key manifestation of Parkinson's disease. L-Dopa, or Levodopa, is often administered to patients having Parkinson's disease, and can have the effect of causing the patient to become dyskinetic for a period of time after administration. As Parkinson's disease progresses, the half life of L-Dopa shortens and the effective dose range decreases, making dosage control extremely difficult and complex. This is commonly managed by increasing the dose frequency, sometimes by as much as ten doses each day in an attempt to control symptoms and enable the patient to have a reasonable quality of life. Thus, patients with Parkinson's disease may experience periods of bradykinesia, dyskinesia and normal motor function several times a day and throughout the course of a single dose of L-Dopa.
Even if a satisfactory dosage regime is reached at one point in time, the progressive nature of Parkinson's disease means that neurologists must regularly review a patient's symptoms in order to effectively control the patient's ongoing treatment dosage. Without objective and ongoing monitoring it is very difficult for physicians to avoid prescribing either an excessive dose which overly increases episodes of dyskinesia, or an inadequate dose which does not prevent episodes of bradykinesia. Furthermore there is no objective measure to say whether a change in dose was effective in improving symptoms.
From clinical observation, skilled neurologists can usually detect the existence of bradykinesia and dyskinesia. In one approach, the observing physician gives a score in the range of 0 to 20 to indicate the severity of the observed episode. FIG. 1 shows scores given by three neurologists, with each plotted point representing the scores given by two neurologists when observing a single dyskinetic episode. Scores for Neurologist 1 (triangles) and Neurologist 3 (circles) are plotted against scores from Neurologist 2. As is evident, the subjective nature of this scoring approach leads to considerable variation. In one extreme example, Neurologist 2 scored one dyskinetic episode as being of severity 10 (being quite severe when noting that the highest score ever given by Neurologist 2 was a 13), whereas Neurologist 3 scored the same episode as being of severity 0 (no dyskinesia observed). Thus, while physicians can usually detect dyskinesia and other kinetic states during observation, these states are not easily quantified, making dosage control very subjective.
Further, clinical observation typically only occurs over a short period of patient attendance, usually of the order of tens of minutes, once every 6 or 8 weeks. Fluctuations in kinetic state throughout the day and from one day to the next significantly complicate attempts at assessing the patient's kinetic state. Clinicians often rely on the patient's recollection and/or written diaries to gain an understanding of the ongoing kinetic state of the patient between clinical appointments. However patients can rarely give objective scores, and the effect of a kinetic episode itself can often make it difficult for a patient to make any record whatsoever of the nature of and timing of motor fluctuations.
Another common symptom, of Parkinson's Disease for example, is tremor. Parkinsonian tremor is slower than most forms of tremor with a frequency of 4-6 cycles per second. Compared with other elements of movement, tremor consists of oscillations of relatively few frequency components. On spectral analysis, it appears as a discrete peak in a narrow frequency range (4-6 Hz), usually clearly above the frequency range of normal movement (less than 4 Hz). Tremor has been the subject of numerous studies and is particularly amenable to study with spectral analysis. Tremor is relatively easy to detect because it is a continuous repetitive movement, giving a sinusoidal signature, which is simple to distinguish from normal human motions which are rarely so continuous. Tremor is far less a problem in management of Parkinson's Disease than dyskinesia and bradykinesia. Attempts have been made to infer a person's bradykinetic state from measurements of tremor, in an attempt to regulate medication. However for many patients there is not a close correlation between tremor and bradykinesia, making it likely that medication will be inaccurately administered using this technique.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.